Subsea pod pump

ABSTRACT

A subsea oil and gas production Christmas tree control system, serviceable by an ROV subsea, comprises an umbilical and a system controller further comprising an HPU that comprises a manipulatable subsea housing; a subsea hydraulic fluid reservoir; a motor disposed in the housing; and a hydraulic power unit disposed in the housing. Hydrocarbon production may controlled subsea by deploying a modular subsea oil and gas production Christmas tree control system using an ROV; supplying the HPU with hydraulic fluid; providing a predetermined control to a subsea Christmas tree using a Christmas tree control system component; monitoring a Christmas tree control system status; enabling a redundant Christmas tree control system component upon detection of a fault in a Christmas tree control system component paired with the redundant component; and providing status data from the Christmas tree control system to a status data receiver using a data communications link.

PRIORITY

This application claims priority through United States Provisional Application 61/413,707 filed Nov. 15, 2010.

FIELD OF THE INVENTION

The invention described herein relates a change in the umbilical architecture of most field developments as only low pressure fluids would need to be delivered to the local subsea distribution manifold or subsea tree. The invention more specifically relates to supplying hydraulic power subsea, and more specifically to a subsea hydraulic power unit that uses a biodegradable fluid for hydraulic motive force.

BACKGROUND OF THE INVENTION

Typical control umbilicals for subsea field developments contain numerous components such as electrical signal and power wires. The actual amount used and the size of any of these depends on the configuration of the field development. Hydraulic supplies, e.g. pumps and storage, are typically located at a surface location as opposed to subsea, necessitating hydraulic supply lines to be included in a control umbilical. In a typical field development, the hydraulic fluid is pressurized by a surface located HPU and vented subsea to sea.

Further, typical field development umbilicals may have chemical lines including dedicated chemical injection hoses for each chemical and for each subsea tree. For example, typically there are two different chemicals used so if there are three subsea trees six lines for chemicals will be required in an umbilical.

As a result, umbilicals are often non-standard as they have to be tailored to the specific subsea site. Field operators are often unable to retrieve susbea modules to service, replace or reconfigure key components utilized in a subsea oil field development, thus decreasing the reliability of such equipment which, in turn, affects oil production. In the past, other solutions have used discrete high pressure hydraulic lines or employed specialty chemical valves. The essence of the invention is the by locating a pump subsea, the pressure is only increased at a local point close to the fluids final destination, The pump also has the added benefit of being able to locally meter or regulate the amount of fluid that is needed or is necessary. An important benefit is that in high pressure umbilicals, much energy is lost due to friction over long distances, a local electric pump using an electric umbilical experiences much less energy losses.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the present invention will become more fully apparent from the following description, appended claims, and accompanying drawings in which:

FIG. 1 is a planar view of an exemplary system in partial perspective;

FIG. 2 is a schematic view of an exemplary system;

FIG. 3 is a cross-sectional view of an exemplary armored cable; and

FIG. 4 illustrates a further embodiment of a portion of the invention illustrating an exemplary HPU module.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1-2, in one embodiment system 1 comprises umbilical 10, HPU module 20, chemical injector module 30, accumulator module 40, low pressure hydraulic module 50, high pressure hydraulic module 60, and electrical module 70. In an embodiment, system 1 further comprises subsea umbilical termination module 80. FIGS. 1-2 illustrate deployment of system 1 in a field further comprising surface structure 100, subsea Christmas trees 4 a-4 d, and other structures for illustration.

Umbilical 10 may comprise lines 12. As other lines needed for subsea control may originate subsea with system 1, e.g. hydraulic lines 2 a-2 d and/or electrical control lines 3 a-3 d, umbilical 10 may be standardized with a set number of lines 12. For example, umbilical 10 may comprise steel tubes, power lines, and fiber optic cables. Further, moving HPU module 20 from the surface, e.g. located at platform 100, to a module subsea may eliminate the need for a hydraulic supply line in umbilical 10.

Chemical injector module 20 may comprise one or more ROV removable chemical injection valves 21 which may further be used for each tree 4 a, 4, 4 c, and 4 d. Therefore, only one chemical line 22 for each chemical used may be required within umbilical 10. In a typical installation, only two chemical lines 22 may be needed for multiple trees.

Referring now to FIG. 3, HPU module 30 is an ROV replaceable module located subsea, comprising at least one pump 32 and one motor 34. In a preferred embodiment, pump 32 comprises one or more piston pumps slaved to one or more electric motors.

In a preferred embodiment, HPU module 30 comprises at least two low pressure sections (not shown in the figures) and at least two high pressure sections (not shown in the figures). These sections are independent of each other and redundant. In an embodiment, if anyone motor 34 or pump 32 begins to malfunction, its secondary motor 34 or pump 32 begins to pick up.

HPU module 30 further comprises instrumentation 36. Instrumentation 36 may comprise one or more sensors, e.g. flow rate, temperature, pressure and/or on/off state sensors which may be used to sense one or more parameters reflecting the performance of pump 32 and/or motor 34.

HPU motor 34 utilizes fluid, typically supplied from reservoir 35. Reservoir 35 may be used to supply fluid to pump 32 and accept return and vent fluid, e.g. from relief valves 37. In a preferred embodiment, system 1 is a closed system and the fluid is a biodegradable hydraulic fluid.

If a leak occurs subsea in system 1, there is a chance of starving pumps 32. Therefore, in a currently envisioned alternative an extra line 12 d (FIG. 4) may be present in umbilical 10 where extra line 12 d may be used to direct and/or replenish fluid in reservoir 35, e.g. up until such time as an ROV can be mobilized and replace a leaking HPU module 30.

Accumulation module 40 may be present and may be an ROV replaceable module containing one or more accumulators 42 (not shown in the figures) such as may be required to dampen the hydraulics. Accumulators 42 may be further used to contain a sufficient supply of fluid to maintain system pressure. Fluid filters 43 (not shown in the figures) may also be located in accumulation module 40. Accumulation module 40 may be charged, e.g. with fluid, from HPU module 30.

Low pressure valve module 50 and high pressure valve module 60 may contain solenoid actuated hydraulic valves, e.g. 52 and 62, required to supply hydraulic control to the various tree valve actuators and tree chokes. Hydraulic valves 52,62 may be controlled from electronics module 70 and may be supplied with hydraulic fluid from accumulation module 40.

In a preferred embodiment, electronics module 70 communicates via fiber optic connection 12 e (FIG. 4) through umbilical 10, e.g. to a surface device such as controller 102 (FIG. 1). Electronics module 70 may comprise electronics to perform several functions, by way of example including decode a multiplexed signal, control HPU module 30, obtain and communicate status for system 1, fire solenoids in low pressure hydraulic valve module 50 and high pressure hydraulic valve module 60, send a signal to change one or more settings on chemical valves in chemical injector valve module 20 (FIG. 1), and the like, or a combination thereof. Electronics module 70 may also handle other instrumentation inputs and outputs, e.g. from other devices whether on trees 4 a-4 d or in system 1.

Long high pressure umbilicals are expensive, many times the cost of this pod, and are more prone to failure the higher the pressure. System 1 reduces the cost and complexity of umbilicals and can be used to meter fluids by specifically controlling amount pumped.

Referring back to FIG. 1, in a further embodiment system 1 is an assembly of components into an ROV operable and replaceable subsea package. This embodiment comprises the primary components: pump 32, electric or hydraulic motor 34, pod carriage 82, and in the case of electric motor, a variable frequency drive VFD 39. This embodiment may be used to increase pressure to hydraulic or chemical fluids, for the purpose of supplying pressure to hydraulic control systems, or chemicals to processes. In the case on hydraulic fluids, system 1 may be configured as a hydraulic power unit, or HPU. When system 1 is configured for chemical delivery, it could be configured as a chemical injection pump. In both cases, the final configuration would differ by the hydraulic connections, fluid filtering, and need for local accumulators, depending on the specific application.

In the operation of an exemplary mode, susbea control of hydrocarbon production devices may be provided by deploying system 1 subsea using an ROV (not shown in the figures). HPU 30, which is part of system 1, then uses a closed loop hydraulic system for its supply of hydraulic fluid. Therefore, although it may have one, umbilical 10 need not have a hydraulic supply line for HPU 30.

Umbilical 10 may be fabricated to be uniform, irrespective of the subsea field device environment. For example, umbilical 10 may have a limited number of chemical lines 12 used to aid in dispersing chemicals to Christmas trees 4 a-4 d may be handled by system 1 susbea. HPU module 30 accepts fluid from reservoir 35. Accumulators 42 in accumulation module 40 may be used to dampen the hydraulics along with contain sufficient supply to maintain system pressure. Accumulators 42 may get their charge/fluid from HPU module 30.

One or more other components of system 1, e.g. low pressure module 50 or high pressure module 60, may be used to provide a predetermined control to a Christmas tree located subsea, e.g. trees 4 a-4 d. 27. These predetermined control may comprise actuation of valves at trees 4 a-4 d using hydraulic controls, actuation of valves at trees 4 a-4 d using electrical controls, chemical injection, or the like, or a combination thereof. For example, valves in high pressure valve module 60 and low pressure valve module 50, e.g. solenoid actuated hydraulic valves, may be used to supply hydraulic control to the various tree valve actuators and tree choke of trees 4 a-4 d. These valves may get their direction and solenoid motivation from electronics module 70. Further, these valves may receive their hydraulic fluid from accumulation module 40.

Redundancy in system 1 allows system 1 to respond to certain faults, providing a time window during which the fault may be fixed while allowing production to be maintained. For example, during operations, one or more predetermined status indicator of system 1 may be monitored such as by using electronics module 70. If a fault is detected in a paired redundant component, e.g. pump 32 a, its redundant component may be enabled and the fault component disabled, e.g. pump 32 a and motor 34 a may be disabled and pump 32 b and motor 34 b enabled, thus allowing production control to be maintained subsea. A failed module, or any other module such as one needing preventive maintenance or upgrading, may be replaced subsea using an ROV.

Status data of system 1 may be monitored, either continually, at predetermined intervals, or upon demand such as from a surface device. These data may then be provided, e.g. either continually, at predetermined intervals, or upon demand, to a predetermined receiver of status data using a data communications line, e.g. fiber optics cable 12 e.

In a preferred mode electronics module 70 utilizes fiber optic cable 12 e for its connection. As fiber optics comprises a large bandwith, system 1 may be able to communicate more data than prior art systems. Use of fiber optics cable 12 e may further allow having a full diagnostics system located subsea. Raw data may be sent back to a surface device, e.g. a computer for additional programming, e.g. double checking diagnostics at the surface.

It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the following claims. 

1. A hydraulic power unit (HPU) for use subsea, comprising: a. a remotely operated vehicle (ROV) manipulatable housing deployable subsea; b. a subsea reservoir of hydraulic fluid; c. a motor disposed in the housing; and d. a hydraulic power unit disposed in the housing, the power unit slaved to the motor and in a closed loop fluid communication with the reservoir.
 2. A subsea oil and gas production Christmas tree control system, serviceable by a remotely operated vehicle (ROV) subsea, comprising: a. an umbilical, further comprising at least one of (i) a predetermined number of chemical lines, (ii) a predetermined number of hydraulic lines, (iii) a predetermined number of electrical power lines, or (iv) a predetermined number of data communication lines; and b. a system controller, further comprising a hydraulic power unit (HPU) module; c. a subsea hydraulic supply reservoir module in closed loop hydraulic system communication with the HPU; and d. a subsea umbilical termination module in fluid communication with the umbilical and the system controller, the subsea umbilical termination module further comprising at least one Christmas tree control line.
 3. A method of providing susbea control of hydrocarbon production devices, comprising: a. deploying a modular subsea oil and gas production Christmas tree control system subsea using remotely operated vehicle (ROV), the Christmas tree control system comprising a hydraulic power unit (HPU) and an umbilical; b. using a closed loop hydraulic system to supply the HPU with hydraulic fluid; c. using a component of the Christmas tree control system to provide a predetermined control to a Christmas tree located subsea; d. monitoring a predetermined status of the Christmas tree control system; e. enabling a redundant component of the Christmas tree control system upon detection of a fault in a component of the Christmas tree control system paired with the redundant component; and f. providing status data from the Christmas tree control system to a predetermined receiver of status data using a data communications link. 